You can’t buy Ripple with a credit card at this time. You will have to buy Bitcoin with a credit card (via CoinMama.com, CEX.io, Coinbase.com or some other site) then exchange the Bitcoin for Ripple (via simple exchange Shapeshift.io or Kraken.com, Poloniex.com, HitBTC.com, etc.).

You will of course need a Ripple wallet to receive your XRP. It’s better to use a personal wallet, like Rippex or even more secure, a Ledger Nano S, than to leave the XRP on exchange.